1. Field of the Invention
The present invention relates generally to infrared signal generating devices and more particularly to an improved micro-scale thermal infrared cell and array particularly suitable for testing infrared sensors.
2. Description of the Related Art
In thermal imaging systems, emitted infrared radiation is imaged on an imaging plane so that the infrared radiation can be converted into electrical signals, typically by a plurality of detectors. The electrical signals are then processed for output on, for example, a display or tangible medium which can be viewed by a user, or utilized by a data processor. Thermal imaging systems are particularly useful in specialized applications where observation of self-emission of objects is desired, e.g., night-time military actions, fire fighting, industrial monitoring, etc. In order to test infrared imaging devices, infrared radiation generating devices must be utilized. It is important during the test phase that such devices evaluate the functional performance of the imaging devices and realistically simulate anticipated operational scenarios. However, this requirement must be balanced against the cost and complexity of the infrared generating device. A number of different types of infrared generating devices for simulating anticipated operational scenarios of thermal imaging systems have been developed or proposed.
Techniques have been developed which significantly improve infrared generating devices for use in system testing and simulating operational scenarios. For example, techniques have been developed to reduce flicker and weight, and to improve the thermal range, response time and efficiency of such devices. Techniques have also been developed for thermally isolating resistive heater elements from the semiconductor substrate of an infrared image generating device.
However, even utilizing the most recently proposed techniques, in order to accurately and realistically simulate anticipated operational scenarios, the emitting area of the resistive element must be relatively large. Accordingly, a substantial amount of power is required to drive the resistive element to produce the infrared radiation necessary for test or simulation of infrared imaging devices. This adds to the cost and complexity of the device. Furthermore, large resistive elements have a relatively large time constant, and take a relatively long period of time to reach the temperature necessary to produce specific infrared radiation, e.g., 600.degree. C., and are thermally less stable than more compact resistive elements. Additionally, because of the large amount of heat which is produced by large resistive elements, control circuitry for driving, controlling and monitoring the infrared generating cells have necessarily been located external from the infrared generating cells. This results in a more cumbersome structure as well as increased signal losses and other deleterious consequences which are well known.